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Sealed enclosures are not tuned to a certain frequency

Posted by Richard BassNut Greene on February 26, 2007 at 09:29:22

In Reply to: Building subwoofer cabinets posted by Beginner on February 26, 2007 at 07:25:38:

Ported enclosures are tuned to a resonant frequency based on the interior volume of the enclosure and the volume of air inside the port (which behaves like a Helmholtz Resonator at a frequency related to those volumes of air). The frequency response of the port rolls off at 24dB/octave on either side of the "tuning frequency".

With sealed enclosures you can "fine tune" the enclosure by adding sound absorbing stuffing of up to 1.25lbs per cubic foot (beyond that density the stuffing becomes counterproductive in large subwoofer enclosures -- small enclosures can use more dense stuffing).

This "tuning" slightly affects the low frequency rolloff of the driver (The speaker's Qtc to be specific).

Since every sealed enclosure should use stuffing to prevent reflections off the back of the enclosure from coming back at your ears though a driver cone, the only question is what density of stuffing to use.

I use inexpensive polyester stuffing at 1.25lbs per square foot for all my large subwoofer enclosures. Fiberglass is more effective, but I'm allergic to it.
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Richard BassNut Greene
Subjective Audiophile 2007

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